General term =38+(n−1)17=17n+21=17(n+1)+4=17k+4 Each term is in the form of 17k+4 Least 3-digit number in the form of 17k+4 is at k=6, i.e. 106 Highest 3-digit number in the form of 17k+4 is at k=58, i.e. 990 106,123,140,..........990 990=106+17(n−1) n=53 Sum =